Warm engine idle fluctuation

[Richard J. Andrews]

temp gauge can cause these problems.
same unit tells computer what temp the engine is

HTH!
rich
86 4kq
At 10:59 PM 12/22/01, you wrote:
>--
>[ Picked text/plain from multipart/alternative ]
>My 1988 90Q idle is about 1200 RPM when fully warmed up. It then starts to
>fluctuate between 1220 and 750 every two seconds. It only remains at 750 for
>an instant. I've changed the idle stabilization valve and squirted WD40
>around vacuum lines with no success. I have been told this could be the O2
>sensor or air control potentiometer. I also wonder about the temperature
>multi-switch on the radiator hose neck. When I disconnect the idle
>stabilization valve and replace the broken vacuum connection, the idle drops
>to 750, leading me to believe the ECU is directing the fluctuation by some
>malfunctioning sensor input. My temperature gauge is also erratic. I have
>been told that there is a vltage regulator located in the gauge panel which
>controls the reference vltage for both the water temp gauge and the fuel
>gauge, which by the way, also does not read full when it actually is full.
>Since the gauge is nothing more than an milliammeter, with a calibrated
>potentiometer float, I would assume a regulated voltage lower than what it
>should be would give a needle deflection of less than it should for a full
>tank. Any comments would be greatly appreciated. Thanks in advance, Ron
>Pellerin